AUDIO MODES AND MULTICHANNEL AC3AC3 audio tracks support up to 6 different channels (L, R, Center, LS, RS, LFE) but MPEG Streamclip can only play/convert two channels at a time. Using the "Audio Mode" pop-up menu you can choose the two channels to be used. If you have no special needs, you can use the default audio mode (Stereo Mix); otherwise, keep on reading for more detailed info.

Stereo MixMakes a mix of L, R, Center (the 3 front channels) plus LS and RS (the 2 surround channels), it takes the mixing coefficients from the AC3 stream and produces a stereo sound in conformance to the A52 standard. The LFE channel is not included.Note that for AC3 2/0 (see below) this and the 3 following modes just pass the L and R channels unchanged.

Front MixIt is the same as Stereo Mix, but it excludes LS and RS (the two surround channels) from the mix. Use it when the surround channels have bad sound.If the surround channels are not present, or were already excluded from the Stereo Mix (due to a zero mixing coefficient from the AC3 stream) then Front Mix produces the same sound as Stereo Mix.

SurroundMakes a Dolby Surround-compatible stereo sound. Using this special stereo sound, a Dolby Pro Logic amplifier with 6 speakers (5+1 subwoofer) may be able to reconstruct and play all the 6 channels of AC3.Use this mode only if your audio equipment has a Pro Logic decoder and can handle Dolby Surround.

L/R Ch.Lets you play and extract the L and R channels as a stereo pair. All other channels are excluded. If both L and R channels are missing, the Center channel is used instead.

Center Ch.Lets you play and extract the Center channel. All other channels are excluded. If the Center channel is missing, a mono mix of L and R is used instead.

LS/RS Ch.Lets you play and extract the LS and RS (surround) channels as a stereo pair. All other channels are excluded. If LS and RS are missing but exists a S (center surround) channel, this channel is used instead. If LS, RS and S are all missing, the sound will mute.

LFE Ch.Lets you play and extract the LFE (low frequency effects) channel, used to drive a subwoofer. This channel is optional even in AC3 3/2; if it's missing, the sound will mute.

You can use the last 4 modes to make 4 AIFF files holding all the content of the AC3 track. You can then put these files into A.Pack to make a new AC3 file with the same content; but make sure to disable A.Pack preprocessing option "Apply 90º Phase-Shift".